Polyurethaneurea elastic fiber is prepared by dry-spinning a polymer obtained by extending prepolymer of isocyanate terminal synthesized by high-molecular polyol and organic diisocyanate using diamine as chain extender, which is cross-knitted with nylon, polyester and natural fiber to be used as an elastic raw material applied in the production of clothes including foundation, socks, panty stocking, and swim suit.
In the structure of polyurethaneurea elastic fiber, hard segments composed of bulky urea groups are linked by hydrogen bond, providing excellent elasticity. But, under the high heat condition, hard segments move out of their places, causing damage on thermo-stability. Thus, when it is cross-knitted with synthetic fiber, which is a high temperature dyeing process, or re-stained or third-dyed for color combination to produce foundation, etc, the elastic fiber of fabric is easily loosed or cut and reducing elasticity of fabric and widened fabric size. This has been a common problem of polyurethaneurea elastic fiber.
Various attempts to improve heat-resistance have been made by polyurethaneurea elastic fiber production companies. Some of them produce fibers with improved heat-resistance, but as heat-resistance improved, other physical properties such as strength, elasticity recovery property, settability, and elasticity were sacrificed or problems in production line have been reported.
If ethylenediamine is independently used as a chain extender for the production of polyurethaneurea to increase elasticity and thermo-stability to commercially satisfactory level during dyeing process of synthetic fiber or re-dyeing or third-dyeing, heat-resistance is satisfactorily increased owing to the linearity of ethylenediamine and strong cohesive force between hard segments. But, the reaction speed of chain extension becomes so fast that side reactions are induced. In addition, such strong cohesive force induces gel generation, suggesting that viscosity of spinning solution becomes unstable, which might cause rapid increase of viscosity that makes spinning difficult or reduces strength and elasticity of elastic fiber.
As an effort to overcome the above problems, Japanese Patent Publication No. S44-22113 describes that a small amount of 1-functional mono-alcohol is used for the production of prepolymer to regulate the reaction speed of chain extension and to inhibit side reactions. But, instead, physical properties of elastic fiber such as strength and elasticity are necessarily sacrificed, which still needs improvement.
The examples of the prior arts for the improvement of heat-resistance of polyurethaneurea elastic fiber are described in Japanese Patent Publication No. S58-59213, and U.S. Pat. No. 5,100,999. According to those descriptions, polycaprolactonediol and polycarbonatediol are used as polyols composing soft segments of polyurethaneurea to give the structure of crystalline cross-linking point stronger to improve heat-resistance. However, the improvement effect was not so great and rather elasticity recovering property was lowered than that of polyurethaneurea using polyetherpolyol.
Japanese Patent Publication No. H1-110520 describes a method to improve heat-resistance by using diaminodiphenylurea as the diamine used as a chain extender. Precisely, in this invention, it was attempted to increase cross-linking density in hard segments of urea group included in the structure of diamine in order to increase heat-resistance. However, cross-linking was induced in pre-spinning polymer solution, resulting in time course changes of viscosity of the spinning solution with reducing stability.
In the meantime, Japanese Patent Publication H4-100919 describes a prior art for improving heat-resistance by using triamine as an additive added after polymerization but before spinning. Since then, many polyurethaneurea elastic fiber production companies tried to improve heat-resistance by using triamine as a chain extender or an additive but the results were not satisfactory. And thus, triamine is used only as a supplement for strength reduced by a co-extender added to improve heat settability. But, viscosity instability of spinning solution is unavoidable by using over-dose of triamine.
Polyurethaneurea elastic fiber is prepared by dry-spinning or melt-spinning a polymer obtained by extending prepolymer of isocyanate terminal synthesized by high-molecular polyol and organic diisocyanate using diamine chain, which is cross-knitted with nylon, polyester and natural fiber to be used as an elastic raw material applied in the production of clothes including foundation, socks, panty stocking, and swim suit.
The polyetherglycol structure composing the soft segments of polymer of polyurethaneurea elastic fiber becomes degraded by chlorine water used for bleaching or active chlorine used for sterilization of swimming pool, resulting in the decrease of physical properties. To improve chlorine-resistance of polyurethaneurea elastic fiber used for swim suit, it has been tried to produce polyurethane elastic fiber using polyesterglycol. However, aliphatic ester is easily attacked by fungi because of its high biological activity and chlorine-resistance thereof is not so good. To improve chlorine-resistance of polyether based polyurethane, diverse chlorine-resistant additives have been tried. Japanese Patent No. S57-29609 and U.S. Pat. No. 4,340,527 describe the use of zinc oxide for the improvement of chlorine-resistance. But, zinc oxide has a problem of being yellow by the reaction with an additive and being eluted during acidic staining (pH 3-4). In particular, the use of zinc component is prohibited by European environment regulations. Japanese Patent No. S59-133248 describes that chlorine-resistance is improved by using hydrotalcite. However, hydrotalcite used as an additive to improve chlorine-resistance is very hygroscopic, so that gel formation and filtering pressure are increased and spinning property is decreased. Japanese Patent No. H91-243446 describes that chlorine-resistance of polyurethaneurea elastic fiber is improved by using hydrotalcite coated with fatty acid to prevent moisture absorption of the anti-chlorine additive and to improve dispersibility. However, hydrotalcite is reacted with an additive added to increase light-resistance and gas-resistance of the fiber, so that the product becomes yellow during spinning and wave is made in the fiber. U.S. Pat. No. 5,626,960 describes the use of huntite-hydromagnesite mixture to improve chlorine-resistance. However, gel formation in polymer resulted from absorption of the anti-chlorine material not coated and poor dispersibility are still problems with this method along with the increase of filtering pressure and the decrease of spinnability, resulting in the color change of the final product to yellow.